In general, as shown in FIG. 1, a High-Definition Multimedia Interface (HDMI) source 102 (e.g., a source of audio and/or video data such as a set-top box, a digital media receiver, an optical media player, etc.) can use a unidirectional interface to transmit audio and/or video data to an HDMI sink 104 so that the audio and/or video data can be presented. As also shown in FIG. 1, audio and/or video data can be transmitted over TMDS channels 106 from an HDMI transmitter 108 of HDMI source 102 to an HDMI receiver 110 of HDMI sink 104, and a signal or signals can be sent from HDMI sink 104 to HDMI source 102 over a hot plug detect (HPD) line 112 to indicate to HDMI source 102 that an HDMI connection has been established between HDMI source 102 and HDMI sink 104.
Certain HDMI sources can use a Consumer Electronic Control (CEC) line 114 to communicate with an HDMI sink and/or one or more other HDMI sources connected in a network via a CEC bus. Messages sent on the CEC bus using CEC line 114 can be addressed to a particular physical and/or logical address of an HDMI device connected to the CEC bus (e.g., as described below). Particular types of messages that comply with the HDMI CEC standard can be sent over the CEC bus to a particular address (e.g., a physical address and/or a logical address) or as a broadcast message to all HDMI devices connected to the CEC bus. For example, messages to control a system volume can be sent over the HDMI bus so that any HDMI device connected to the CEC bus can control the volume of the system. The volume controls specified by the HDMI standard include, for example, volume up, volume down, mute, and unmute.
However, the HDMI standard only allows for discrete volume control, such as volume up or volume down, and does not include an instruction for setting a system volume level to a specific level (e.g., as a percentage of the maximum volume).
Accordingly, it is desirable to provide methods, systems and media for controlling audio of an HDMI audio system.